My Ignatius Catholic Study Bible goes into a lot of background and says that Jesus portrayed the church as a spiritual temple. Hell or Hades is,
the place of the dead where souls descend through it's gates. It is not hell but a temporary realm where souls are detained until the last judgement. By extension, Hades is also the habitation of evil forces that bring about death and deception
Further down it describes Jewish tradition in regards a stone as the foundation of the Temple. From this background it states,
The Temple, resting securely on a rock, was thus the center of the cosmos, the junction between heaven and Hades. Drawing from this background, Jesus guarantees that the powers of death and deception will not overcome the church-i.e., the new temple built on Peter. He enables Peter (and his successors) to hold error at bay and faitfully proclaim the gospel
There is an imprimatur for the study bible so I think this description can be counted on to be accurate. However, there was a lot of background given for that passage that I didn't include because it was too extensive to type here.